Vertical Hall sensors typically comprise a Hall effect region that is formed within a substrate, such as a semiconductor substrate. Vertical Hall sensors respond to magnetic field components parallel to the substrate or, more precisely, parallel to a main surface of the substrate.
Typically, vertical Hall sensors have one problem in common, namely an offset error. The offset is the output signal in the absence of the magnetic field (component) which the sensor should detect. The origin of the offset error is basically a slight asymmetry of the device. This asymmetry can be caused by asymmetry in the geometrical shape (which of course one tries to avoid). Yet, even in the case of perfect or near perfect geometrical asymmetry, the electrical potential distribution in the device causes an asymmetry, due to the junction field-effect. The junction field-effect is caused by the fact that a Hall sensor typically comprises a Hall effect region that is formed as a tub of opposite doping type than the surrounding substrate. Accordingly, the active region (i.e., the Hall effect region) of the Hall sensor is limited by a small pn-junction which causes the Hall sensor to exhibit a field effect transistor-like behavior. The junction field-effect causes nonlinearities and limits the maximal achievable value of magnetic sensitivity.